The invention relates to techniques for reducing deposits in plasma etch reactors.
Current semiconductor processing equipment, including plasma reactors (both etch and chemical vapor deposition (CVD) type), create non-volatile byproducts that deposit on the chamber walls. These byproducts change the chemical composition of the chamber wall. Build-up of these deposits can cause process drift, particle contamination, and a short chamber maintenance cycle because of the necessity for frequent wet cleans.
During processing of semiconductor wafers it is conventional to carry out periodic in-situ cleaning of plasma etch and CVD reactors to alleviate the above mentioned problems. U.S. Pat. No. 5,129,958 discloses a method for cleaning a CVD deposition chamber in a semiconductor wafer processing apparatus wherein fluorine residues in the chamber, left from a prior fluorine plasma cleaning step, are contacted with one or more reducing gases such as silane (SiH4), ammonia, hydrogen, phosphine (PH3), diborine (B2H6), and arsine (AsH3). Another technique for cleaning and conditioning interior surfaces of plasma CVD reactors is disclosed in commonly owned U.S. Pat. No. 5,647,953, the subject matter of which is hereby incorporated by reference. In the past these cleans were done with a wafer in the chamber to cover the electrode, but it has become more common to do waferless cleans.
Other techniques for cleaning plasma reaction chambers are disclosed in U.S. Pat. Nos. 4,657,616; 4,786,352; 4,816,113; 4,842,683, 4,857,139; 5,006,192; 5,129,958; 5,158,644 and 5,207,836 and in Japanese Laid-Open Patent Publication Nos. 57-201016; 61-250185, 62-214175, 63-267430 and 3-62520, and in commonly owned U.S. Pat. No. 5,356,478. For instance, in order to remove SiOX deposits, a fluorine-containing gas energized into a plasma has been used to clean interior surfaces of the chamber. Fluorine residues remaining after the reactor cleaning can be removed by passing a reducing gas such as hydrogen (H2), silane (SiH4), ammonia (NH4), phosphine (PH3), biborine (B2H6) or arsine (AsH3) through the reactor.
In process chambers that etch aluminum metal, some of the byproduct can be composed of aluminum fluoride or other solid material consisting in part of aluminum and fluorine atoms. While an aluminum etch chamber requiring an etch process that uses a fluorine-containing gas (e.g., CF4, CHF3) is one example of a source that may produce aluminum fluoride, other processes can as well. Since many processing chambers are constructed of aluminum metal, almost any process that uses a fluorine-containing gas can produce aluminum fluoride. A process to eliminate aluminum fluoride from the chamber would reduce the incidence of defects, chamber processing drift, and/or chamber downtime for cleaning and maintenance.
This invention provides a method of cleaning a plasma etch chamber in which substrates are processed, comprising the steps of introducing a cleaning gas comprising a chlorine-containing gas into the chamber, energizing the cleaning gas into a plasma state, forming dissociated and undissociated reactive species in the chamber and reacting these species with deposits on the interior surfaces of the chamber. After the cleaning step, a conditioning step may be performed.
In a first preferred embodiment, a method of cleaning aluminum fluoride deposits from a plasma reaction chamber after etching a semiconductor substrate is provided. A cleaning gas comprising at least BCl3 is supplied to a plasma etch reactor. When energized into a plasma state, the cleaning gas forms dissociated and undissociated BCl3 and the undissociated BCl3 reacts with aluminum fluoride deposits in the plasma etch reactor and cleans the deposits from the interior surfaces. The cleaning gas may comprise BCl3/O2 or BCl3+Cl2/O2 wherein a concentration of Cl2 may be supplied to obtain a desired degree of BCl3 dissociation.
In a second preferred embodiment, a method of reducing aluminum fluoride deposits from a plasma reaction chamber during plasma etching of a semiconductor substrate is provided. The etching step includes a main etch and an overetch. An etching gas during the main etch includes CxFyHz wherein xxe2x89xa71, yxe2x89xa71 and zxe2x89xa70 and aluminum fluoride deposits are formed during the main etch. The etching gas during the overetch includes at least BCl3 which is energized into a plasma state and forms dissociated and undissociated BCl3. During the over etch, the undissociated BCl3 reduces the aluminum fluoride deposits in the plasma etch reactor. Subsequent to the etching step, the substrate can be removed from the plasma etch reactor and a cleaning step can be carried out. The cleaning gas may comprise O2, Cl2/O2, BCl3/O2 or BCl3+Cl2/O2 wherein a concentration of Cl2, may be supplied to obtain a desired degree of BCl3 dissociation.
It is further provided that the method may include a plasma etching step in which a main etching gas comprising CxFyHz wherein xxe2x89xa71, yxe2x89xa71, and zxe2x89xa70, Cl2, N2 and BCl3 and an over etching gas comprising Cl2 and BCl3 is utilized to etch a semiconductor wafer.